Boris Johnson today slammed "barmy" health and safety rules after a London couple were threatened with being referred to social services for letting their children cycle to school.

Oliver and Gillian Schonrock have come under fire for allowing their eight-year-old daughter and five-year-old son to cycle the mile-long journey from their home in West Dulwich to Alleyn's Junior School.

The headmaster at the £12,000 a-year private school, Mark O'Donnell, has told the parents it would be forced to contact the local authority if the school felt the children were in danger.

But the Schonrocks said they simply wanted their children to learn about "the risks of life". The Mayor hailed the couple as "heroes".

In his weekly column for the Daily Telegraph, Mr Johnson said: "They have taken the sword of common sense to the great bloated encephalopathic sacred cow of 'elf and safety."

He said the school's threat to refer the parents to social services was "utterly barmy".

"The fundamental point is that this is the business of the parents and not that of the state. If Mr and Mrs Schonrock have carefully assessed the route then they should overwhelmingly be given the benefit of the doubt and the freedom to make up their own minds."

Mr Schonrock, 40, a managing director of an e-commerce company said they wanted to let their children enjoy life and understand its risks. He said: "Like everybody else we spent a lot more time with our friends playing in the streets or parks without parental supervision and without our parents becoming unduly worried."

Headteachers cautioned against schools assuming legal responsibility for children as they travel to school.

Andrew Grant, head of St Albans School and chairman of the Headmasters and Headmistresses' Conference, said: "There has to come a point where we have to give people the opportunity to exercise their own judgment."

However, neighbours of the couple criticised the family. Joanna Gilbert, 41, said she would not let her six-year-old daughter or eight-year-old son cycle the route. She said: "I would not trust them to walk on their own let alone cycle."

Mr O'Donnell said: "If a school feels a child in their care is at risk, they have a legal responsibility to notify the local authority. Is an eight-year-old responsible enough to come to school with a five-year-old and take responsibility when it comes to crossing the road?"

The parents have now been told they must accompany the children or be referred to children's services.